Kitchen Stove Vent


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Old 11-20-14, 08:16 AM
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Kitchen Stove Vent

I'd like to install a vent for my kitchen stove. I'm just getting started and have a few questions. According to code, what's the minimum duct size I can use and how far can it run? I'm guessing like dryer vents there are a limit to how many turns you can make.

The wall adjacent to the stove is shared on the other side by a bathroom wall. Does code allow me to tap into the bathroom vent as an exhaust? Perhaps I could put some kind of one-way damper to keep the smoke from going into the bathroom? I have a brick house and would really like to use the same exhaust.

Any information on how to install a kitchen stove vent or what code says about it would be very helpful.

Thanks!
 
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Old 11-20-14, 09:14 AM
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In many areas a vent is not required so there is no code for the duct size. The duct size is usually dictated by the vent hood/fan you choose. Also, the length of duct and number of bends is dictated by the hood/fan you choose. Some can push air over a longer distance while inexpensive models can't handle much resistance and their flow is dramatically reduced by a long duct run.

No, you cannot connect a kitchen exhaust vent into the bathroom vent. Most bath vents use 4" line while kitchen exhaust fans usually require 6" or larger. Also, because of the risk of fire the kitchen vent should be rigid steel. If the material is not specified by your local codes most vent hood manufacturers will specify steel ducting.

You will most likely have to run your exhaust duct straight up. It's common for the duct to run through the cabinet above the stove and into the attic and through the roof or some other exhaust location. The next question then is how will you power the hood? Will you run a new circuit or tie into an existing one?
 
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Old 11-20-14, 09:44 AM
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Pilot Dane,
Thanks for the information. I need to start looking at the fans and hoods and reading what they require.

Too bad I can't use the bathroom vent, although I understand the justification. However, I'd much rather vent to the side of my house than through the roof.. There's another story above the kitchen. When you say "most likely" are you referring to code or to the manufacturer's instructions?

As for how to power it, I can't imagine having to run an entirely new circuit just to run a lousy exhaust fan. Certainly code doesn't require this?

That said I am thinking about greater kitchen renovation in the future. I know you have to have a dedicated circuit for the microwave, and I know all outlets need to be GFCI, but what else should I be aware of? Do lights have to be on their on circuit? Does the fridge, dishwasher, or other appliances require their own circuit? (I have a gas stove). 20 amp for everything except lights? In terms of space and amperage I'm pushing my electrical box pretty hard as it is...

Thanks again for your time and advice.
 
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Old 11-20-14, 11:23 AM
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There's another story above the kitchen. When you say "most likely" are you referring to code or to the manufacturer's instructions?
Usually a mixture. Code generally says follow manufacturers instructions but code must also be followed. Ultimately all code is local. The national is just a template for the local code which may or may not be an altered version.
I can't imagine having to run an entirely new circuit
It can be run on the lighting circuit if it is not too heavily loaded. It can not be run on one of the dedicated 20 amp kitchen counter receptacle circuits (SABC).
I know you have to have a dedicated circuit for the microwave
Only if fixed in place like a combined hood and microwave over the stove.
Do lights have to be on their on circuit?
No they can be with other lighting circuits. They can not be on the SABC (counter top receptacle circuit). Gas stoves can be plugged into a SABC receptacle. dishwasher and garbage disposal can share a circuit but not one of the small appliance receptacle circuit.

Code requires at least two dedicated 20 amp Small Appliance Branch Circuits for receptacles (AKA SABC, AKA counter top receptacles).

A vent for the exhaust hood might be able to be run through the cabinets to an outside wall depending on layout of your kitchen.
 
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Old 11-21-14, 07:32 AM
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Thank again for all this guidance. Of course I'll look into this a lot more before doing any work, but it's good to have an idea what I'm in for.

Let me make sure I understand. So one circuit for the light, but I can share this circuit with other lights on the same floor (15 amp)

One circuit for the microwave (countertop), dishwasher, garbage disposal, 20 amp. But can I share this circuit with other outlets on the same floor but not in kitchen?

Vent can be run on either of the above. Gas stove anything but lighting.

But then I need TWO MORE for the counter top outlets that cannot be used by the built in appliances mentioned above? (all gfci, 20 amps) But can I share these with other outlets on the same floor? Living room lamp or something...

So at minimum, I'm supposed to have four separate circuits coming into the kitchen? Lights, 2 for counter tops (SABC), one for other build in appliances/microwave?

I was hoping to run the vents through the subfloor in such a way as to not compromise the joists, saving me cabinet space. The wall the stove is on is perpendicular to the exterior wall where I would want to vent it, so I'd say it's about a 7' run. I assume I would only want the vent to run laterally or up.

Also, although I've never really used one, I've heard about these drawer mounted microwaves. I've got almost no interest in these, but I'm curious what kind of reputation they have.

Thanks!
 
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Old 11-21-14, 11:07 AM
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The dedicated circuits are just that. Dedicated to each's purpose and not shared. The 20 amp dedicated kitchen counter receptacle circuit is for the kitchen counter outlets and can not power outlets or fixtures in other rooms.

Are you considering counter downdraft vent? If not I would not run the vent line down. I suppose it could be done but most hoods vent out the top and the 180 bend to go down would really hurt the flow and you'd need to convert to a rectangular duct to fit inside the stud bay. Down draft vents often run through the floor but many of them require even larger ducts as the need to move a lot more air and still are not very effective.

Running a vent duct laterally through a wall is generally not an option as the duct is larger than the wall is thick. This would require cutting or removing all the studs leaving no structure. That's why the duct is often run straight up through the cabinet above and into the attic where there are less things in the way.
 
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Old 11-21-14, 11:43 AM
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So one circuit for the light, but I can share this circuit with other lights on the same floor (15 amp)
Or another floor.
One circuit for the microwave (countertop), dishwasher, garbage disposal, 20 amp.
No, DW/GD on separate circuit.
But can I share this circuit with other outlets on the same floor but not in kitchen?
No, kitchen and dining room only.
Vent can be run on either of the above.
No. It shouldn't be on the DW/GD circuit and can't be on the SABC.
 
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Old 11-23-14, 06:09 AM
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Ray,
Okay, thanks. I guess I should look at the microwave on the counter top as just another Small Appliance.

I really appreciate the advice and help from you and pilot dane. Have a good one!
 
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Old 11-23-14, 08:15 AM
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I'm learning from Ray's responses as well.
 
 

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